Air-core Fiber Research Articles

Interstitial Optical Fiber-Mediated Multimodal Phototheranostics Based on an Aggregation-Induced NIR-II Emission Luminogen for Orthotopic Breast Cancer Treatment.

One-for-all phototheranostics based on a single molecule is recognized as a convenient approach for cancer treatment, whose efficacy relies on precise lesion localization through multimodal imaging, coupled with the efficient exertion of phototherapy. To unleash the full potential of phototheranostics, advancement in both phototheranostic agents and light delivery methods is essential. Herein, an integrated strategy combining a versatile molecule featuring aggregation-induced emission, namely tBuTTBD, with a modified optical fiber to realize comprehensive tumor diagnosis and "inside-out" irradiation in the orthotopic breast tumor, is proposed for the first time. Attributed to the intense donor-acceptor interaction, highly distorted conformation, abundant molecular rotors, and loose intermolecular packing upon aggregation, tBuTTBD can synchronously undergo second near-infrared (NIR-II) fluorescence emission, photothermal and photodynamic generation under laser irradiation, contributing to a trimodal NIR-II fluorescence-photoacoustic (PA)-photothermal imaging-guided phototherapy. The tumor treatment is further carried out following the insertion of a modified optical fiber, which is fabricated by splicing a flat-end fiber with an air-core fiber. This configuration aims to enable effective in situ phototherapy by maximizing energy utilization for therapeutic benefits. This work not only enriches the palette of NIR-II phototheranostic agents but also provides valuable insight for exploring an integrated phototheranostic protocol for practical cancer treatment.

Vibration-insensitive polarimetric fiber optic current sensor based on orbital angular momentum modes in an air-core optical fiber.

Current or magnetic field sensing is usually achieved by exploiting the Faraday effect of an optical material combined with an interferometric probe that provides the sensitivity. Being interferometric in nature, such sensors are typically sensitive to several other environmental parameters such as vibrations and mechanical disturbances, which, however, inevitably impose the inaccuracy and instability of the detection. Here we demonstrate a polarimetric fiber optic current sensor based on orbital angular momentum modes of an air-core optical fiber. In the fiber, spin-orbit interactions imply that the circular birefringence, which is sensitive to applied currents or resultant magnetic fields, is naturally resilient to mechanical vibrations. The sensor, which effectively measures polarization rotation at the output of a fiber in a magnetic field, exhibits high linearity in the measured signal versus the applied current that induces the magnetic field, with a sensitivity of 0.00128 rad/A and a noise limit of 1×10-5/H z. The measured polarization varies within only ±0.1% under mechanical vibrations with the frequency of up to 800 Hz, validating the robust environmental performance of the sensor.

Finding the superior mode basis for mode-division multiplexing: a comparison of spatial modes in air-core fiber

Finding the superior mode basis for mode-division multiplexing: a comparison of spatial modes in air-core fiber

Soliton pulse compression in air-core photonic band-gap fibre

Soliton pulse compression in air-core photonic band-gap fibre

Design and Simulation of Air-Core Polymeric Photonic Crystal Fiber by Investigating the Reduction of Confinement Losses in the Terahertz (THz) Range

Design and Simulation of Air-Core Polymeric Photonic Crystal Fiber by Investigating the Reduction of Confinement Losses in the Terahertz (THz) Range

Trench-assisted multi-ring-core fiber for orbital angular momentum modes

Orbital angular momentum (OAM) multiplexing technology has attracted significant interest due to its ability to increase the data transmission capacity in optical communications. By combining OAM-based mode division multiplexing (MDM) and wavelength division multiplexing (WDM) techniques in multi-core fiber (MCF), the transmission rate and spectral efficiency of the optical communication systems can be greatly enhanced. In this paper, we present a design of a multi-ring air-core trench-assisted fiber that supports transmission over the entire C + L (1530–1625 nm) band with low inter-ring crosstalk. The high-contrast ring and trench design can effectively suppress the inter-modal crosstalk. The effects of the ring spacing, wavelength range and doping concentration on the crosstalk suppression are also systematically investigated. Furthermore, the complexity of the MIMO processing system is greatly reduced with a fewer-optical-core structure while keeping low inter-ring crosstalk. The results demonstrate that our designed fiber can support 140 OAM modes at 1550 nm with < −79.4 dB inter-ring crosstalk at low Ge-doped concentration (12.5 mol%), and it can keep the inter-ring crosstalk below −66.56 dB across the C + L band, which features lower inter-ring crosstalk than the other reports while supporting more OAM modes. Furthermore, to support more OAM modes with lower inter-ring crosstalk and intra-modal crosstalk, we further provide a second low-doping-concentration (12.5 mol%) fiber design, which can support 196 OAM modes with < −35.74 dB inter-ring crosstalk and Δneff > 5.39 × 10−4. Additionally, our designed fiber can support 224 OAM modes (37.5 mol% Ge-doped) and < −63 dB inter-ring crosstalk with low intra-modal crosstalk (Δneff > 5.45 × 10−4) and flat dispersion distribution (chromatic dispersion slope lower than 0.171 ps/nm2/km) across the C + L band.

Reconfigurable structured light generation and its coupling to air–core fiber

Recently, structured light beams have attracted substantial attention in many applications, including optical communications, imaging, optical tweezers, and quantum optics. We propose and experimentally demonstrate a reconfigurable structured light beam generator in order to generate diverse structured light beams with adjustable beam types, beam orders, and beam sizes. By controlling the sizes of generated free-space structured light beams, free-space orbital angular momentum (OAM) beams and vector beams are coupled into an air–core fiber. To verify that our structured light generator enables generating structured light with high beam quality, polarization distributions and mode purity of generated OAM beams and vector beams in both free space and air–core fiber are characterized. Such a structured light generator may pave the way for future applications based on higher-order structured light beams.

Retracted: Interferometric Air-Core Anti-Resonant Fiber Optic Gyroscope With Enhanced Thermal Stability

The use of a quadrupolar-wound coil of conjoined-tube anti-resonant fiber (CTF) in an interferometric air-core fiber optic gyroscope (FOG) is proposed and demonstrated. The CTF coil has low transmission loss and high modal purity, resulting in a long-term bias stability of 0.016 deg/h for the integration time of 1000 s. Furthermore, when compared to a gyro operated with conventional polarization-maintaining fiber (PMF) coil of the same length and diameter, the conjoined-tube anti-resonant fiber optic gyroscope (CTFOG) has an 11.2-fold reduction in thermal sensitivity, rendering the CTF a promising technological approach to efficiently improve the thermal stability of FOG in the future.

Orbital Angular Momentum in Fibers

Orbital angular momentum (OAM) of light beams with helical phase front, as an alternative spatial dimension resource of photons, has attracted extensive attention over the past decades. Very recently, OAM in fibers has facilitated rapid development of various fiber-based applications, such as optical communications, optical manipulation, optical sensing, optical imaging, nonlinear optics, and quantum science. Comprehensive and in-depth understanding of OAM in fibers is of great interest to researchers in this area. Here, we give a tutorial overview of OAM in fibers. We first introduce the basic theories, including the eigenmode analysis method, mode coupling theory, and spin-orbit mapping of light in fibers. We then give a detailed classification of OAM fibers and discuss versatile spatial mode bases in fibers. After that, we review various OAM fiber designs, including conventional single-mode fibers, conventional multi-mode fibers, ring-core fibers, air-core fibers, photonic crystal fibers, negative-curvature hollow-core fibers, multi-core fibers, active fibers (e.g., erbium-doped fibers), etc. Besides, we describe the state-of-the-art commercial fiber manufacturing processes as well as testing and characterization methods for OAM fibers. We also review various active and passive OAM fiber devices. Moreover, we introduce several typical advanced applications based on OAM fibers, such as capacity scaling fiber-optic communications, remote vectorial Doppler velocimetry, super-resolution optical imaging, and high-dimensional quantum cryptography. Finally, we briefly discuss future challenges and prospects of OAM in fibers.

Remote Measurement of the Angular Velocity Vector Based on Vectorial Doppler Effect Using Air-Core Optical Fiber.

Rotational Doppler effect has made tremendous development in both theoretical and applied research over the last decade. Different from the inertial thinking of focusing on the scalar field dominated by helical phase light, we have revealed a vectorial Doppler effect in our previous work, which is based on the spatially variant polarized light fields to simultaneously acquire the speed and direction of a target. Here, further, we propose a method to construct a flexible and robust velocimeter based on that novel effect by employing an air-core fiber with kilometer-length scale for remotely measuring the vectorial information of angular velocity in situ. In addition, we experimentally substantiate that the measurement system still has commendable accuracy in determining the direction of movement even when the air-core fiber is interfered by the external environment. The demonstrations prove the potential of vectorial Doppler effect in practical scenarios and remote measurements.

Seven air-core fibers with germanium-doped high-index rings supporting hundreds of OAM modes

In this paper, we propose and design a multi-orbital-angular-momentum multi-ring air-core fiber, which has seven high-index rings with each ring supporting 62 radially fundamental OAM modes across C and L bands (from 1530 nm to 1625 nm), i.e. 434 OAM modes in total. The designed fiber features >4×10-4 intra-ring modal indices difference for OAM modes with the same topological charge l in a ring across the C and L bands. Moreover, it can keep <-52 dB crosstalk between the OAM modes in the adjacent rings at 1550 nm, and <-24 dB crosstalk across C and L bands after 100-km fiber propagation. This kind of seven-air-core-ring fiber would be a robust candidate for transmitting efficient OAM modes and boosting the capacity of optical fiber communications systems.

Preface

The 2021 2nd International Conference on Electrical, Electronic Information and Communication Engineering (EEICE 2021) was successfully held online through Zoom on April 16-18, 2021. Due to COVID-19 and the pandemic-related nationwide lockdowns and other coordinated restrictive measures, the organizers decided to hold a conference in a virtual format with the organization of access for all participants to the presented reports with comprehensive discussion for ensuring the event at a high scientific level.EEICE 2021 is to bring together innovative academics and industrial experts in the field of “Electrical”, “Electronic Information”, “Communication Engineering” and “Communication and Information System”, etc to a common forum. The primary goal of the conference is to promote research and developmental activities in “Electronic Information Technology”, “Communication Engineering” and another goal is to promote scientific information interchange between researchers, developers, engineers, students, and practitioners working all around the world.This scientific event brings together more than 125 national and international researchers in Electrical, Electronic Information and Communication Engineering. On top of the local participants coming from different national universities, international participants are also registered from different countries, namely Iran, Italy, Denmark and USA. During the conference, the conference model wasdivided into three sessions, including oral presentations, keynote speeches, and online Q&A discussion. In the first part, some scholars, whose submissions were selected as the excellent papers, were given about 5-10 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches.In the second part, we invited four professors as our keynote speakers. Prof. WONG Hei, from Department of Electrical Engineering, City University of Hong Kong performed a speech: Device, System, and Application Prospectives of More Moore and More than Moore. This talk highlighted some of these issues with some personal remarks and prospective on the technology development in coming decades, in particular with 5G mobile technology to be introduced. And then we had Prof. Yang Yue from Institute of Modern Optics, Nankai University, China. He presented an insightful speech: Air-Core Ring Fiber Supporting Numerous Optical Orbital Angular Momentum Modes. Another two keynote speakers were Prof. Ting Yang, from School of Electrical and Information Engineering, Tianjin University, China and Prof. Wenli Shang, from School of Electronics and Communication Engineering, Guangzhou University, China. Their insightful speeches had triggered heated discussion in the third session of the conference. Every participant praised this conference for disseminating useful and insightful knowledge.The proceedings are a compilation of the accepted papers and represent an interesting outcome of the conference. Topics include but are not limited to the following areas: Electrical Engineering, Electronic Information, Communication Engineering and more related topics. All the papers have been through rigorous review and process to meet the requirements of International publication standard.We would like to acknowledge all of those who supported EEICE 2021. The help and contribution of each individual and institution was instrumental in the success of the conference. In particular, we would like to thank the organizing committee for its valuable inputs in shaping the conference program and reviewing the submitted papers.Committee of EEICE 2021Committee member, Conference Chairman, Organizing Committees, Technical Program Committees and this titles are available in this pdf.

Air-Core Non-Zero Dispersion-Shifted Fiber With High-Index Ring for OAM Mode

It is well-known now that orbital angular momentum (OAM) modes can be a potential technology to take full advantages of the space resources in the fiber-based optical communication system because of its infinite states. However, the corresponding fiber design for OAM modes to meet various requirements in the fiber-based communication system is still not enough. For the dispersion property, there are various attributes given in the standard of ITU-T series, which has not yet been proposed for the OAM modes. In this paper, we propose and design a non-zero dispersion-shifted air-core ring fiber for OAM mode, which can offer more options on dispersion values. A negative dispersion of -1.246 ps/(nm·km) or a positive dispersion of 1.541 ps/(nm ·km) at 1550 nm with <; 1.5 ps/(nm ·km) dispersion variation across the C band or <; 4 ps/(nm ·km) dispersion variation across the C and L bands for OAM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1,1</sub> mode is achieved in the numerical simulation.

Air-Core Ring Fiber Guiding &gt;400 Radially Fundamental OAM Modes Across S + C + L Bands

In this paper, we propose and design a Ge-doped air-core ring fiber, which can support a large amount of OAM modes for mode-division multiplexing (MDM) in optical fiber communications. By varying the mole fraction of GeO2 and adjusting the structure parameter, including the air-core radius and the GeO2-doped ring width, we investigate the influence of different fiber parameters on the total supported OAM mode number. The hollow silica fiber with a 50- $\mu \text{m}$ air core and a 1.5- $\mu \text{m}$ thickness of Ge-doped ring is designed in simulation to support fiber eigenmodes up to HE112,1 and EH107,1. This provides 436 OAM modes at 1550 nm while maintaining radially single mode condition. Moreover, it can support more than 400 radially fundamental OAM modes for the wavelength from 1460 nm to 1625 nm, covering entire S, C and L bands. The optical parameters of the guided OAM modes in the fiber are also numerically analyzed, including effect of material loss, optical field distribution, effective refractive index profile and chromatic dispersion, etc. The simulation results show that the higher-order OAM modes have longer $2\pi $ and 10-ps walk-off length in the air-core ring fiber with ellipticity or bending compared with low-order modes.

Vortex Polymer Optical Fiber with 64 Stable OAM States.

This research introduces a numerical design of an air-core vortex polymer optical fiber in cyclic transparent optical polymer (CYTOP) that propagates 32 orbital angular momentum (OAM) modes, i.e., it may support up to 64 stable OAM-states considering left- and right-handed circular polarizations. This fiber seeks to be an alternative to increase the capacity of short-range optical communication systems multiplexed by modes, in agreement with the high demand of low-cost, insensitive-to-bending and easy-to-handle fibers similar to others optical fibers fabricated in polymers. This novel fiber possesses unique characteristics: a diameter of 50 µm that would allow a high mechanical compatibility with commercially available polymer optical fibers, a difference of effective index between neighbor OAM modes of around 10−4 over a bandwidth from 1 to 1.6 µm, propagation losses of approximately 15 × 10−3 dB/m for all OAM modes, and a very low dispersion for OAM higher order modes (±l = 16) of up to +2.5 ps/km-nm compared with OAM lower order modes at a telecom wavelength of 1.3 µm, in which the CYTOP exhibits a minimal attenuation. The spectra of mutual coupling coefficients between modes are computed considering small bends of up to 3 cm of radius and slight ellipticity in the ring of up to 5%. Results show lower-charge weights for higher order OAM modes.

Stable Excitation of Orbital Angular Momentum States in Air-Core Fiber Seeded by an Integrated Optical Vortex Beam Emitter

We experimentally demonstrate excitation of orbital angular momentum states in an air-core fiber by a silicon integrated vortex beam emitter which is designed and fabricated to match the modes supported by the fiber. The coupling loss is measured to be ∼7.5 dB. Excitation of eigenmodes is confirmed by analyzing the fiber output.

An air-core photonic crystal fiber based plasmonic sensor for high refractive index sensing

Most surface plasmon resonance (SPR) based photonic crystal fiber (PCF) sensors have been designed to detect the analyte refractive index (RI) ranging from 1.33 to 1.41. In this paper, we propose a new approach to extend the detection range of the sensor, and it can be fabricated with the existing fabrication techniques. Contrary to the existing PCF based sensors, our designed sensor is based on an air-core PCF where analyte is placed to the core of the PCF through a vertical side opening channel and is able to detect RI of the analyte higher than that of the PCF background. We use a chemically stable plasmonic material (i.e., gold), where the plasmonic material and analyte are placed in such a way that there is no direct contact between them, thus reducing the interference effect. According to our simulation, we show that the spectral sensitivity and resolution are achieved as 11,700 nm/RIU and 8.55×10−6 RIU, respectively, for the analyte RI of 1.42. We believe that our proposed sensor can be used to detect highly active chemical and biological liquid samples.

Beyond Two-Octave Coherent OAM Supercontinuum Generation in Air-Core As2S3 Ring Fiber

In this work, we designed and simulated a novel air-core As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ring fiber that supports orbital angular momentum (OAM) modes. By optimizing the structure parameters of the designed fiber to effectively tailor its chromatic dispersion, a near-zero flat dispersion profile with a total of <; ±30 ps/nm/km variation over 3380-nm bandwidth from 2025 nm to 5405 nm is achieved for OAM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1,1</sub> mode. After launching a 100-fs 70-kW hyperbolic secant pulse into an 8-mm air-core As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ring fiber, a light-carrying OAM supercontinuum is numerically formed beyond two-octave range, covering 5717nm bandwidth from 1182 nm to 6897 nm at -30dB. Furthermore, the generated supercontinuum is highly coherent across the whole spectral range. This can serve as an effective manner to expand the spectral coverage of the OAM beams for various applications.

Two-Octave Supercontinuum Generation of High-Order OAM Modes in Air-Core As₂S₃ Ring Fiber

In this work, we design and simulate an air-core As 2 S 3 ring fiber for high-order orbital angular momentum (OAM) supercontinuum generation. We show that the chromatic dispersion of the ring fiber can be substantially tailored by proper optimization of the air-core radius. Two-octave supercontinuum carrying OAM 17,1 mode, spanning from 1560 to 6250 nm, is obtained by pumping a 50-fs 100-kW secant hyperbolic pulse centered at the wavelength of 3800 nm into the designed fiber with 50-μm air-core radius and 1-μm ring width. We further engineer the chromatic dispersion of some other OAM modes and perform simulations of supercontinuum spectra using different kilowatt-level peak power, which indicates that the fiber we design represents a promising avenue for supercontinuum generation of all the OAM l,1 modes (|l| ≤17). The proposed fiber is suitable for the transmission of OAM beams in infrared wavelength range and it could promote the development and application of high-order OAM beams.

Air-Core Ring Fiber With &gt;1000 Radially Fundamental OAM Modes Across O, E, S, C, and L Bands

In this work, an air-core ring fiber is designed with a record high 1322 orbital angular momentum (OAM) modes at 1550 nm while maintaining radially single-mode condition. Moreover, it can support over 1004 OAM modes across all O, E, S, C, and L bands, exploiting to our knowledge the highest number of OAM modes ever supported in the optical fiber within a wide wavelength range. Simulations show that, across the C and L bands, the fiber with 55-μm air-core radius and 0.45-μm ring width can preserve 3.3 × 10 -3 effective refraction index difference between the two highest-order OAM modes HE 340,1 and EH 271,1 . This enables efficient mode separation, and thus achieving stable OAM modes transmission. The effective refractive index differences between the even and odd fiber eigenmodes are also analyzed in the elliptical and bent fibers. We note that higher-order OAM modes are more tolerant to the fiber ellipticity and bending. This ring fiber design has the potential to increase the spectral efficiency and the overall capacity in fiber-based communications system.